Making wines with a lower alcohol content basically comes down to four options, each with different pros and cons. These are:
- Put less sugar in. Alcohol is made from sugar during fermentation – put less sugary grapes in and inevitably there will be less alcohol. Sounds fine, but will low sugar grapes also have all the other attractive favours that give a wine its particular characteristics?
- Convert less of the sugar. If the fermentation process is less efficient at converting the sugar then again less alcohol will be made. But will a less efficient process also make all the flavours you want to keep? And does the remaining sugar make the wine too sweet?
- Take the alcohol out afterwards. Again sounds good, but the removal process will also remove some of the flavours and aromas you wanted to keep.
- Dilute the alcohol afterwards, typically with grape juice or just water.
And remember, less alcohol will inevitably change the wine. Alcohol in particular gives the wine its “body” – a lower alcohol wine will be lighter in every sense. Nonetheless, how well do each of these four approaches work?
Growing grapes with less sugar is achieved in two main ways; grow them somewhere with less sunshine (so further from the equator and on steep hillsides) and make the vine less effective at producing sugar in the grapes. This can be done by reducing the number of leaves on the vine, relative to the weight of grapes – it is the leaves that produce the sugar which gets concentrated in the grapes. Thus most naturally low alcohol wines come from higher latitude areas with more cloud, such as northern Germany, coastal Portugal or New Zealand (pictured). Or they are the product of careful growers who trim the leaves off their vines with great precision.
Controlling the fermentation so that the conversion of the sugar into alcohol in the fermentation is reduced also calls for great expertise from the producer. They can select a yeast which is less effective, but doing so may also change the flavour of the wine produced – a yeast can be as characteristic of its region as the grapes. And next they can shorten or slow the fermentation process so that less conversion is done by keeping it cool at 13-15 °C. This is called low temperature fermentation and in addition the process can be arrested the moment the desired ABV is reached. The downside here is if excess sugar remains in the wine this will make it sweeter – a primary characteristic of many lower alcohol wines. Muscat or Moscato wines are the one most commonly made in this way.
Alternately wine makers can remove the alcohol from a wine after fermentation. This has the benefit that a full fermentation has been completed so all the normal flavours, body and aromas have been produced. The trick remaining is to get the alcohol out without removing anything else. Two processes have been industrialised for high volume use. The first is “Spinning Cone” method which is a form of low temperature vacuum steam distillation under which the alcohol is vapourised off the wine. It is good in that it runs at low temperature and so mistreats the wine less, but it requires large scale industrial plants and it still risks that some aromas are also vapourised and lost during the process. But it works pretty well and many wines today are being put through this process, typically to reduce them from say a natural 16% ABV which the fermentation produces to a more standardised 14%. However, our experience seems to suggest that if the ABV is taken down to zero, or even to around 5%, then a lot of flavour is lost.
The second common dealcoholisation process used today is “Reverse Osmosis” by which the wine is repeatedly run over a semi-permeable membrane through which the smaller water and alcohol molecules can pass, leaving behind the bigger body and aroma flavour molecules. This process is more suited to smaller scale production but has the downside that some wanted smaller molecules such as for the aroma will also be lost through the membrane. There are ways to recover them but this will not be perfect. In general, this process seems less commonly used than Spinning Cone.
The final tool open to the wine maker is to simply dilute the full strength wine with something non-alcoholic, of which grape juice is the most common. This is simple to do but legally fraught and very difficult to execute well without producing a drink equally diluted in taste. In general, this seems to be little used.
With the above suite of tools, many wine makers are setting about manipulating their wines even to produce our “full strength” wines, as producers struggle to stop the continuous rising of ABVs that is coming from global warming producing ever more sugary grapes. Great progress has been made. We are particularly enthusiastic about producers simply growing the grapes with less sugar. Most of our 5-Star wines have been made this way. But no one has yet found a way to perfectly give a wine back the body and aroma it loses from having its alcohol removed or diluted. Generally the results are very mixed – for example some sparkling whites work really well whilst most reds are atrocious.